Drain Valve Assembly for Use in an Air Compressor System

ABSTRACT

The present air compressor system includes an inlet connected to a compression stage, a cooling stage having an inlet connected to an outlet of the compression stage and having an outlet passage; a drain valve having an liquid inlet in and adjacent a bottom of the outlet passage of the cooling stage to drain condensation when opened; and a controller controlling the compression stage and the drain valve.

BACKGROUND AND SUMMARY OF THE INVENTION

The present disclosure relates generally to air compressors and more specifically to a drain valve for an air compressor.

An air compressor, for example, two-stage air compressors include a first low pressure compression stage connected through an inter-cooling stage through high pressure compression stage whose output is provided through an after cooling stage to an air reservoir. Any condensation is generally removed at the air reservoir as indicated, for example, in FIG. 1 of U.S. Pat. No. 6,027,311 and U.S. Pat. No. 4,453,893. Each of the compressor stages produces a pressure dew point that is higher than atmospheric dew point. Condensation occurs when the output of the cooler drops temperature below the pressure dew point. If the condensation is not removed at temperatures above freezing, the moist air will cause problems in the elements after the cooler. This is particularly critical in the inter-cooling stage wherein the air is input into a second compressor stage. If condensation is not removed at or below freezing, the moisture can potentially block the exit of the cooling stages. This is also true at the output of the final or after cooling stage.

One suggestion, as described in U.S. Pat. No. 6,952,932, is to bypass the after cooling stage such that gases are used to heat the cooled gases when ambient temperatures is at or below freezing, and are used downstream from the after cooling stage when moisture freezes in the after cooling stage.

It is well-known in the multistage air compressors to have unloading valves at the output of the inter-cooling stage as illustrated by U.S. Pat. No. 6,287,085 and at the output of the after cooling stage as illustrated in U.S. Pat. No. 4,819,123.

The present air compressor system includes an inlet connected to a compression stage, a cooling stage having an inlet connected to an outlet of the compression stage and having an outlet passage; a drain valve having a liquid inlet in and adjacent a bottom of the outlet passage of the cooling stage to drain condensation when opened; and a controller controlling the compression stage and the drain valve.

A liquid inlet of the drain valve is at the lowest point in the outlet passage. The liquid inlet may be an end of a siphon tube in the outlet passage of the cooling stage. The drain valve includes an air port connected to the outlet passage of the cooling stage whereby air passing from the air port to the drain through the open drain valve educes liquid from the outlet passage of the cooling stage through the siphon. The air port is higher than an end of the siphon connected to the outlet passage of the cooling stage.

The system may include first and second compression stages and the cooling stage is the inter-cooling stage. The cooling stage is connected to an outlet of the first compression stage and the outlet passage of the cooling stage is connected to an inlet of the second compression stage. The drain valve may be connected between the inter-cooling stage and the second compression stage. Alternatively, the drain valve may be connected to the after cooling stage which is connected to the outlet passage of the second compression stage.

A drain valve assembly for an air compressor system includes a housing having a passage extending between a first port and a second port; a valve chamber having a liquid inlet in and adjacent a bottom of the passage and having a drain outlet; a valve seat in the valve chamber between the drain outlet and the liquid inlet; and a valve element responsive to an input signal to cover and uncover the valve seat.

The liquid inlet may be an end of a siphon tube in the passage. The valve chamber includes an air port connected to the passage whereby air passing from the air port to the drain outlet through the open valve seat educes liquid from the passage through the siphon. The air port is higher than an end of the siphon connected to the passage. The valve seat is higher than the liquid inlet.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a compressor system according to the prior art.

FIG. 2 is a perspective view of a drain valve assembly for an inter-cooling stage according the present disclosure.

FIG. 3 is a cross-sectional view of a drain valve assembly taken along lines 3-3 of FIG. 2.

FIG. 4 is a partial cut-away side view of a drain valve assembly for an after cooling stage according the present disclosure.

FIG. 5 is a schematic of a compressor system according to the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A piston compressor of the prior art is illustrated in FIG. 1 as a two-stage compressor unit 10. A drive unit 12 is mounted thereto and may be, for example, an electric motor. The crankcase 13 includes three piston cylinders 14 a, 14 b, and 14 c. The first stage of compression includes piston cylinders 14 b and 14 c receiving air through filter 15. The second high-pressure stage is performed by piston cylinder 14 a. The compressor unit 10 includes a cooling system 16 having an output 17 of the compressed air. Output 17 is generally connected to a reservoir 90 (shown in FIG. 5).

The cooling system 16 for the two-stage compressor includes an inter-cooling stage 20 and an after cooling stage 22. The inter-cooling stage 20 has an inlet (not shown) connected by pipe 24 from the outlet of piston cylinders 14 b and 14 c to the inter-cooling stage 20. Outlet 25 of inter-cooling stage 20 is connected via outlet passage 26 to the inlet of the second stage piston cylinder 14 a. The output of the second stage piston cylinder 14 a is connected via pipe 28 to an inlet of the after cooling stage 22.

As previously discussed, condensation will collect in the inter-cooling stage outlet passage 26, as well as exiting from outlet 17 of the after cooling stage 22. This collected condensation will freeze at lower temperatures and impede the operation of the compressor.

A drain valve assembly 30, illustrated in FIG. 2 or 3, is designed to be connected between the outlet 25 of the inter-cooling stage and the inlet passage 26 of the high pressure stage of piston cylinder 14 a. This would replace pipe 26 of FIG. 1 and be connected at the lower plugged outlet 27 of the inter-cooling stage 20, shown in FIG. 1. The drain valve 40 includes a housing 32 having a passage 38 between ports 34 and 36. Flanges 33 and 35 are provided to connect the ports 34 and 36 to the inter-cooling stage and the second stage compressor, respectively. Appropriate fasteners perform the connection. Housing portion 32 includes a drain valve 40 accessible via cover 39.

By connecting port 34 of passage 38 at the lower outlet 27 of the inter-cooling stage, the bottom 37 of passage 38, which is an extension of the outlet passage of the inter-cooling stage 20 outlet, is below the inlet to the compressor stage 14 a. Thus, this part of the passage 38 is the natural collection point for all condensation in the inter-cooling stage 20 outlet passage. The area adjacent the drain valve 40 is lower than the ports 34 and 36 to form a well to collect the condensation.

The drain valve 40 includes a valve chamber 42 which includes a valve seat 44 mounted therein. Valve element 46 covers and uncovers the valve seat 44 to open and close the drain valve. An air inlet 48 connects the passage 38 to the valve chamber 42. A liquid inlet 50 is at the end of a tube 52 which is also connected to the valve chamber 42. Tube 52 forms a siphon as will be described. The end or the liquid inlet 50 is in the passage 38 and adjacent the bottom 39 of the passage 38. It should also be noted that the liquid inlet 50 is below the height of the valve seat 44. The air inlet 48 is above the valve seat 44. Alternatively, the valve seat 44 may be below the liquid inlet 50 and the tube 52 being replaced with a passage in the wall of the passage 38 connecting the passage 38 to the valve chamber 42. A drain sleeve 54 is threaded into opening 56 of the housing 38 below the valve seat 44.

Since the air outlet of the inter-cooling stage is pressurized, when the valve 40 is open, the air will rush through air inlet 48 and through the open valve seat 44. Such an action induces or creates a vacuum to siphon the liquid resting on the bottom 39 of passage 38 up through the siphon tube 52 and into the valve chamber 42 where it exists the open valve 40. When the valve 40 is closed with valve element 42 on valve seat 44, the pressure in chamber 40 is the same as the pressure in the passage 38 and has none or little effect on moving any of the condensate liquid on the floor 39 of passage 38 into the valve chamber 42.

Although a pneumatic control of the drain valve 40 is illustrated, a solenoid control may be provided. The valve element 46 is controlled by a signal from controller 92 shown in FIG. 5. This may be the same controller that controllers drive 12 of the compressor stage 14 a. As is well known, the drain valve 40 and other unloading valves if present are operated at appropriate times in the cycling of the drive 12.

Piston 60 is mounted in piston chambers 62, which is separated from the valve chamber 42 by sleeve 64. Valve element 46 is mounted to the piston 60 by a fastener 66. A control port 68 in housing 38 provides the input signal to the valve chamber 62 via passage 65 in sleeve 64 to the bottom of the piston chamber 62 below piston 60 to raise it against a spring 70 to open the valve 40. The spring 70 biases the piston 60 to the down position closing the drain valve 40.

As shown in FIG. 2, a heater 72 is provided in the housing portion 38 adjacent the drain valve 40. This prevents, when activated, the freezing of any condensation liquid on the bottom 39 of passage 38 and the valve chamber 42. This will prevent blocking of inlet 50 of the tube 52 as well as obstructing the passage 38 and the drain valve 40. The heater 72 may be thermostatically controlled locally or controlled from the same controller as the motor and drain valve, remotely.

A drain valve with its housing 32 adapted for connection at the outlet of the after cooling stage 22 is illustrated in FIG. 4. Those elements having the same functions or structures have the same number as that in FIGS. 2 and 3. The difference in housing 32 is that the inlets 34 and 36 are in line. A basin may be provided in the passage 38 adjacent the water inlet 50 to create a low collection area or well for the condensation similar to that in FIGS. 2 and 3. Flange 33 would be connected to outlet 27 of the after cooling stage 22. Connected to flange 35 or the outlet of the drain valve 30 is a check valve 80 having inlet 82 and 84 and respective flanges 81 and 83. The outlet 84 of the check valve 80 is connected by flange 83 to piping or other connections to a reservoir 90 shown in FIG. 5. The check valve 80 includes a valve seat 86 and a valve element 88. A spring 70 received in thread cap 92 forces the check valve 88 closed. Initially, the pressure out of the compressor at outlet 17 opens check valve 88. Once the reservoir 90 fills or the pressure is substantially equalized, the check valve 88 closes. The differential is determined by spring 70.

The operation of the drain valves 30 in both embodiments is controlled by the controller 92 which also controls the compressor by controlling drive 12 as shown in FIG. 5. When the motor 12 is stopped either finally or due to cycling the controller 62 will activate the drain valve 40 to drain the fluid at the outlets of the respective cooling stages. The drain valve 40 also operates to depressurize the outlets. The drain valves 40 may be open only enough to drain the condensation liquid at the outlets of the cooling stage without fully unloading the cooling stage outlets. Alternatively, they may also be kept open long enough to operate as an unloading valve. As discussed in the patents above, this unloads the pressure of the various stages of the compressor allowing it to start up against no back pressure in the system. The check valve 80 at the outlet of the after cooling stage 17 of the cooling stage 20 prevents the opening of the drain valve 30 from also depressurizing the reservoir 90 connected to its outlet 84.

Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. Two drain valves 30 may be connected to the outlet of each cooling stage, 20, 22 or at the outlet of only one cooling stage. The scope of the present invention is to be limited only by the terms of the appended claims. 

1. An air compressor system comprising: an inlet connected to a compression stage, a cooling stage having an inlet connected to an outlet of the compression stage and an outlet passage; a drain valve having a liquid inlet in and adjacent a bottom of the outlet passage of the cooling stage to drain condensation from the outlet passage when opened; and a controller controlling the compression stage and the drain valve.
 2. The system of claim 1, wherein the liquid inlet of the drain valve is a siphon tube having an end adjacent a bottom of the outlet passage of the cooling stage.
 3. The system of claim 2, wherein the drain valve includes an air port connected to the outlet passage of the cooling stage whereby air passing from the air port to the drain through the open drain valve educes liquid from the outlet of the cooling stage through the siphon.
 4. The system of claim 3, wherein the air port is higher than the end of the siphon in the outlet passage of the cooling stage.
 5. The system of claim 1, wherein the system includes first and second compression stages and the cooling stage is the inter-cooling stage, and the inlet of the cooling stage is connected to an outlet of the first compression stage and the outlet passage of the cooling stage is connected to an inlet of the second compression stage.
 6. The system of claim 1, wherein the system includes first and second compression stages, and the inlet of the cooling stage is connected to an outlet passage of the second compression stage.
 7. The system of claim 1, including a check valve connecting the outlet passage of the cooling stage to a reservoir, and the drain valve is connected between the cooling stage and the check valve.
 8. The system of claim 1, wherein the drain valve is mounted in a pipe connected to and forming part of the outlet passage of the cooling stage, and the liquid inlet is in and adjacent a bottom of the pipe.
 9. The system of claim 8, the pipe is connected to the outlet passage of the cooling stage so that the bottom of the pipe adjacent the liquid inlet of the drain valve is the lowest point in the outlet passage.
 10. The system of claim 1, wherein a valve seat of the drain valve is higher than the liquid inlet.
 11. The system of claim 1, including a heater mounted adjacent the drain valve.
 12. The system of claim 1, wherein the controller operates the drain valve as an unloading valve for the compressor stage.
 13. The system of claim 1, wherein the drain valve is a pneumatic piston valve.
 14. The system of claim 1, wherein the drain valve is a solenoid valve.
 15. A drain valve assembly for an air compressor system, the drain valve assembly comprising: a housing having a passage extending between a first and second port; a valve chamber having a liquid inlet in and adjacent a bottom of the passage and having a drain outlet; a valve seat in the valve chamber between the drain outlet and the liquid inlet; a valve element responsive to an input signal to cover and uncover the valve seat.
 16. The assembly of claim 15, wherein the liquid inlet is an end of a siphon tube adjacent a bottom of the passage.
 17. The assembly of claim 16, wherein the valve chamber includes an air port connected to the passage whereby air passing from the air port to the drain outlet through the open valve seat educes liquid from the passage through the siphon.
 18. The assembly of claim 17, wherein the air port is higher than an end of the siphon connected to the passage.
 19. The system of claim 15, wherein the valve seat is higher than the liquid inlet.
 20. The system of claim 15, including a heater mounted to the housing adjacent the passage. 